Mobile work holder



July 9, 1963 J. H. PAIGE ETAL 3,096,890

' MOBILE WORK HOLDER Filed April 5, 1960 3 Sheetfs-Sheet l ,Zajw

y 1963 J. H. PAIGE ETAL 3,096,890

MOBILE WORK HOLDER Filed April 5, 1960 3' Sheets-Sheet 2 y 1963 J'. H. PAIGE ETAL 3,096,390

MOBILE WORK HOLDER Filed April 5, 1960 3 Sheets-Sheet 3 United States Patent Ofiiice gfi fifl il Patented July 9, 1963 3,096,890 MOBKLE WORK HOLDER James H. Paige, Rolling Hills, and John L. Wells, La

Canada, Calif, assignors to Fabrodynamics, Inc., Gardena, Calif a corporation of California Filed Apr. 5, 196%, Ser. No. 20,138 6 tClaims. (Cl. 214-4) This invention relates to means for holding a workpiece in position for assembly operations, for example, to hold a chassis of an electronic device. More particularly, the invention is directed to the problem of constructing such an adjustable means to support a heavy workpiece for moving progressively along an assembly line.

Work holders are commonly used to hold workpieces adjustably in convenient positions for sequential operations along assembly lines. Quite often most of the workers are women. In many instances the combined weight of a small workpiece plus that of the work holder on which it is mounted is so small that even a frail woman can easily lift and maneuver the combination. The present invention is concerned with other situations, however, where the workpiece is so heavy and bulky that it requires a workholder that rides on. wheels.

The problem to be met is to provide such a wheeled workholder that will support a large workpiece in an adequately adjustable manner and, most important, do so with foolproof safety. The adjustability should make the workpiece readily maneuverable for free access from various directions, as required for rapid assembly operations with minimum fatigue. Maximum safety can be achieved, of course, by keeping the workpiece lying in one stable position on a low, stable carriage throughout the assembly run. Serious hazards arise, however, when provision is made to support the workpiece at a position that is spaced substantially above the carriage and is also otlset laterally from the carriage to keep the carriage from interfering with the worker. Further serious hazards are incurred when further provision is made for raising and lowering the workpiece for convenient access at difierent stages in the fabrication procedure.

One hazard to be \dealt with is the tendency of the offset weight of the workpiece to tip the carriage over in the direction of the worker. A second serious hazard is that in the procedure of raising and lowering the workpiece to different levels the adjustable holding must be temponarily loosened to transfer the whole weight to the worker so that the worker may lift or lower the workpiece to the desired new level. If the workers grasp on the uncontrolled workpiece fails, or if the worker loses his balance, or if the weight is too great for the workers strength, the worker may be seriously injured. The present invention eliminates these hazards. It provides foolproof safeguards, and does so without sacrificing the desired maneuverability of the workpiece.

To make sure that the offset weight of the workpiece does not tip the carriage towards the worker, the carriage is mounted on a track having three surfaces in three different planes for rolling contact by three different sets of wheels of the carriage. One set of wheels traverses a horizontal track surface to carry a substantial, if not major, portion of the weight. A second set of wheels traverses a track surface that is substantially perpendicular to the lateral load component created by the offset position of the workpiece relative to the carriage, and thus eliminates any possibility of the carriage tipping over towards the worker.

A third set of wheels rolls along a surface in a third plane, to serve a number of purposes. One purpose is to resist any forces directed toward the side of the carriage away from the worker. Another purpose is to stabilize the carriage. A third purpose is to cooperate with flanges of the track to guide the carriage on a straight line and to keep the carriage sufficiently confined to avoid inadvertent derailing of the carriage.

The hazard of the possibility of the worker losing control of the workpiece while he is manually raising or lowering the workpiece is avoided by two safety provisions. One provision is a step-by-step adjustment mecha nism which limits the freedom for movement of the workpiece to only one increment or small step at a time and that requires separate manipulation for each step. If the worker were to release the workpiece entirely in the course of an adjustment, the workpiece would be quickly checked automatically against falling more than an insignificant distance.

The other safety provision is to make the step-by-step adjustment mechanism operable by a foot pedal. This provision leaves both hands free to grasp the workpiece without interruption during the change in elevation of the workpiece.

The various features and advantages of the invention will be apparent from the following detailed description together with the accompanying drawings.

In the drawings, which are to be regarded as merely illustrative:

FIG. 1 is a perspective view of a selected embodiment of the invention;

FIG. 2 is a side elevation of the worker holder carriage used in FIG. 1, showing the manner in which the various wheels of the carriage engage various longitudinal surfaces of the track;

FIG. 3 is a side elevational view of the whole work holder with the track shown in phantom;

FIG. 4 is a front elevational view of the work holder with omission of the upwardly extending yoke to which the workpiece is releasably attached;

FIG. 5 is a fragmentary View on an enlarged scale showing the adjustment mechanism for step-by-step change in elevation of the workpiece;

FIG. 6 is a similar view of a portion of the mechanism at a different stage in the step-by-step operation;

FIG. 7 is a perspective view of a pawl that is used in the step-by-step mechanism;

FIG. 8 is a fragmentary view, partly in section and partly in plan, showing a means for releasably latching the upwardly extending yoke at various positions of rotation; and

FIG. 9 is .a sectional view taken as indicated by the line 9-9 of FIG. 4.

FIG. 1 shows a track structure which is made in sections to be positioned end to end to form as -long an assembly line as may be desired. Each of the sections is mounted on a plurality of pedestals Ill reinforced by braces 12. Each section of the track structure includes an electrical conduit 14 to provide current for energizing devices required along the assembly line, such as soldering irons, lamps, testing devices, etc. The two ends of the electrical conduit 14 of a section of track structure are equipped with electrical fittings for electrically interconnecting the sections. FIG. 1 shows such a fitting in the form of an electrical receptacle 15 at one end of the conduit of the section, the other end of the conduit being equipped with a suitable electric fitting (not shown) for plugging into such a receptacle.

While such a track structure may provide only a single track, the particular track structure shown in FIG. 1 provides two tracks on its opposite sides for two independent parallel assembly lines at considerable saving in space. The structure to form the two tracks may be of the construction shown, which includes two longitudinal channel members 16 at the opposite longitudinal side edges of the structure, two longitudinal inwardly inclined angular panels 13 connected to the two channel members, respectively, a central angular top plate 2% and internal U-shaped reinforcement means 22.

Each of the two trachson the two longitudinal sides of the track structure provides three longitudinal track surfaces, namely: a first longitudinal track surface 24 with an adjacent upstanding flange 25 along the outer longitudinal edge of the track; a second canted downwardly facing longitudinal track surface 26 with an adjacent downwardly extending longitudinal flange 28; and a third canted laterally outwardly facing longitudinal track surface 3%.

The principal parts of a mobile work holder for use on one of the two described tracks include: a movable base or carriage 32 equipped with suitable wheels for engaging the track; an upwardly extending holder in the form of a yoke, generally designated'34, having a spaced pair of upwardly extending arms 35 to straddle and hold a workpiece W; a bearing means $6 with its axis extending upward to journal the yoke for adjustment rotation about the axis, the yoke being mova-bly mounted on the carriage 32 to swing through an arc for adjustment of the yoke 34 at various angles of inclination laterally outward away from. the track; a latch member in the form of a plunger 32 carried by the bearing means 36 to releasably hold the yoke34 at selected positions cf rotation relative to the bearing means; afoot pedal 40 to actuate the latch plunger 33 to permit change in the position of the yoke about the axis of the bearing means; a pair of arcuate rack means, each generally designated R, fixedly carried by the bearing means 36 on opposite sides of its axis; acorresponding pair of pawls 42 on opposite sides of the carriage 32 for cooperation with the two rack means, respectively, to hold the bearing means 36 at selected'angles of inclination and to limit the changes in inclinationof the bearing means to a step by step operation; a foot pedal 44 to operate the two pawls 42. simultaneously and clamp means 45 on the carriage 32 to releasably engage the track structure for immobilizing the carriage when desired.

The yoke 34 includes a crosspiece 46 on which the two arms 35 are slidably mounted for adjustment. Each of the two slidable arms carries a screw 48 (FlG.' 3) with a knob 50 for convenient manualoperation, which screw may be tightened to secure the arm at any desired'position of adjustment on the crosspiece 46. Rotatably mounted on the upper end of each of the yoke arms 35 is a bracket 52 to which one side of the workpiece W may be suitably attached or clamped. Eachof the rotatable brackets 52 may be immobilized by tightening rotation of a correspondingly knurled knob 54.

The 'crosspiece 46 of the yoke 34 is centrally mounted by screws 55 on the upper end of a stub shaft 56 (FIG. 8), which is journaled in thebearing means 36 and is keyed to a disc 58. The disc 58 is rotatably mounted inside a cylindrical skirt 60 of the bearing means. As indicated in FIG. 8, the disc 58 has a plurality of radially directed tapered bores-6 2 for releasable engagement by the previously mentioned latch plunger 38. The latch plunger 38 is slidably mounted in a boss of the cylindrical skirt 60 and is controlled by the previously mentioned downwardly extending foot pedal '40.

The foot pedal 40 is'fixedly mounted on a crosspin 68 that is journ-aled in a pair of ears '70 which extend outward from the skirt 60. The latch plunger 38 is cut away to form a neck portion 72, and the upper end of the foot pedal' 40 is forked to straddle the neck portion and thus operatively engage the latch plunger. A suitable torque spring 74 has one end connected to the crosspin 68 and has its other end in engagement with one of the ears '70 to urge the crosspin in the rotary direction for yieldingly holding the latch plunger 38 in any one of the tapered bores 62.

The cylindrical skirt 60 of the bearing means 36 is formed with a pair of opposite downwardly extending ears 75 for the purpose of pivotally mounting the bearing means on the carriage 32 for tilting movement of the yoke 34 through an are extending laterally from the carriage. The carriage 32 is formed with a corresponding pair of cars '76 that are paired with the cars 75 of the bearing means. Each pair of ears 75 and '76 is provided with a pivot pin '78 which serves-as a trunnion for the bearing means 36.

The carriage 32 may be an open rectangular casting having a pair of opposite side webs fit) which are interconnected by a rear upper web 32 and by a forward lower web A first wheel means comprises two wheels S5 positioned in tandem and mounted on the lower web 84 by axles 86 to roll along the previously mentioned first longitudinal surface 24 of the track. A second wheel means comprises two wheels 58 mounted in tandem on the rear web 52 by suitable axle means to roll along the previously mentioned downwardly facing second longitudinal track surface 26. A third wheel means comprises two wheels 9% positioned in tandem and also suitably mounted on the rear web $2 to roll along the previously mentioned outwardly facing third longitudinal track surface 30.

The previously mentioned clamp means 45 may comprise an angular bracket 92 fixedly mounted on the carriage 32 to overhang the top plate 20 of the track structure. Fixedly mounted on the angular bracket 92 is a nut 94 in which a screw 95 is threaded. The screw 95 is provided with a knob 96 for convenient manual rotation. It is apparent that when the screw 95 is tightened against the top plate 20 of the track structure it cooperates with the pair of wheels 88 to grip the top plate 20 and thereby immobilize the carriage.

Each of the two rack means R that are fixedly mounted on the bearing means 36 on opposite sides of the bearing axis may be of the construction shown in FIG. 5. Each rack means comprises an arcuate rack 1100 in the form of a plate having a peripheral series of spaced rack teeth 102 for engagement selectively by the corresponding pawl 42. Fixedly related to the arcuate rack is a second plate 104 which provides an arcuate series of cam elements 105 overhanging the rack teeth 102.

Each of the pawls 42 for cooperating with a rack means R may be of the construction best shown in FIG. 7. The pawl means in FIG. 7 is a metal bar with a longitudinal extension 106 of reduced cross section for cooperation with the rack teeth 102 and the cam elements 105. Each pawl 42 has a transverse bore 108 to receive a pivot pin 110 (FIG. 4) by means of which the pawl is pivotally mounted in a slot 112 (FIG. 2) of the carriage 32. Each pawl is tapped and bored to receive a set screw 114 (FIG. 7) to serve as an adjustable stop at the lower limit posi tion of the pawl. A suitable torque spring 115 (FIG. 4) is associated with each of the pawls 42 to urge the pawl extension 106 downward towards the arcuate rack 100.

As heretofore stated, the two pawls 42 may be operated by a foot pedal 44. In this embodiment of the invention the foot pedal 44 is a stirrup that is suspended at its opposite ends trorn the respective pawls 42 by means of slender rods 116. The upper ends of the rods 116 are bent to right angles as shown in FIG. 3, and are jouInaled in transverse bores .118 (FIG. 7) in the pawls 42.

The manner in which the invention operates to serve its purpose may be readily understood from the foregoing description. It is apparent that the major portion of the load is carried by the pair of tandem wheels 85 and that the tendency of the yoke to tilt the carriage 32 laterally away from the track is met by the thrust of the pair of tandem wheels 88 upward against the longitudinal track surface 26 under the top plate 20 of the track structure. The third set of tandem wheels 90 in rolling contact with the third track surface 30 resists any tendency for 1the carriage 32 to tilt laterally inwardly towards the trac l The wheels 90 in cooperation with the track surface 30 also serve to maintain the tandem wheels 33 adjacent the overhanging track flange 28 and to maintain the pair of tandem wheels 85 adjacent the upstanding track flange 25. It is apparent that by reason of the two track flanges 25 and 28 the carriage 32 is confined by the track with sufiicient effectiveness to prevent inadvertent derailing of the carriage.

The arms 35 of the yoke 34 are adjustable in spacing to accommodate the dimension of any particular workpiece and when a workpiece is mounted on the two brackets 52 the two knobs 54 may be loosened to permit the workpiece to be rotated about the axis through the two knobs.

When the carriage 32 reaches a station along the assembly line, the clamp means 45 may be actuated to immobilize the carriage for an assembly operation. The knob 96 is conveniently accessible to the operator for this purpose.

If the operator desires to rotate the workpiece about the upright axis of the yoke 34, it is merely necessary for him to exert foot pressure against the downwardly depending pedal 40 to withdrawn the latching longer 38 temporarily out of engagement with the rotary disc 58. Thus the provision of the foot pedal 40 leaves both hands of the operator free to rotate the workpiece to a new position where the latch plunger 38 again engages a tapered bore 62 of the rotary disc 58 to hold the yoke against rotation.

Normally each of the two pawls 42 is in engagement with a selected rack tooth 192 to maintain the yoke 34 at a selected angle relative to the carriage 32. If the operator desires to change the inclination of the yoke to change the elevation of the work-piece, he grasps the workpiece with two hands to support the workpiece and with one foot depresses the pedal 44 to lift the two pawls 42 out of engagement with the arcuate rack 100 for manual shift of the workpiece to the desired new level. if the workpiece is to be lowered, each of the arcuate racks 100 will be rotated clockwise as viewed in FIG. 5. When a pawl 42 is lifited clear of a rack tooth 102, it enters the path of movement of the cam elements 195 as shown in FIG. 6. Consequently, the downward swinging movement of the bearing means 36 causes re next approaching cam element 105 to cam the pawl 42 back towards the arcuate rack 100 into the path of the next successive rack tooth 102. Thus the cam elements cooperate with the pawl and rack to limit the lowering of the heavy workpiece to a step by step movement in which the workpiece cannot fall freely more than a small increment of its range of vertical adjustment.

If the workpiece is shifted from one level to a higher level, the arcuate rack and the associated cam elements 155 are shi ted counter-clockwise as viewed in FIG. 5. To permit this counter-clockwise movement, the operator exerts lifting force on the workpiece to cause the two arcuate racks 102 to shifit counterclockwise and thereby cause the two pawls -42 to ride up the sloping shoulders 120 of the successive rack teeth 102. If desire, the operator may exert light foot pressure on the pedal 44 to reduce or eliminate frictional resistance of the two pawls to the clockwise shift of the arcuate rack. It is apparent that if the operator should inadvertently release the workpiece during this step of elevating the workpiece, the workpiece would be immediately checked against falling by engagement of the pawls with the rack teeth. If one of the two rack-andpawl mechanisms were to tail, the other would safely carry the load.

Our description in specific detail of the selected embodiment of the invention will suggest various changes, substitutions and other departures from our disclosure within the spirit and scope of the appended claims.

We claim:

1. A mobile work holder to adjustably hold a workpiece for movement from station to station along an assembly line, comprising: a track extending along the assembly line; means extending upward from said carriage to support a workpiece, said upwardly extending means being movable about a pivot axis relative to the carriage through a range of angles outward to one side of the carriage; a pair of arcuate racks concentric to said pivot axis, said racks facing each other in spaced relation to form an arcuate space between the racks, said racks respectively presenting sets of teeth on the opposite sides respectively of said arcuate space with the teeth of the two sets staggered; pawl means in said arcuate space movable along the arcuate space to engage said sets of teeth alternately to releasably hold said upwardly extending means at selected angles in said range; and a foot pedal to operate said pawl means for step-by-step adjustment of said upwardly extending means through said range.

2. A work holder to adjustably hold a workpiece, comprising: a base; an upwardly extending holder means to hold the workpiece; means to support said upwardly extending holder means on said base, said supporting means being mounted on the base to move about a pivot axis through a range of angles relative to the base to vary the level of the workpiece; an arcuate toothed rack means on said support means concentric to said axis; pawl means on said base to releasably engage the teeth of said rack means, said pawl means being biased to its engagement position; a foot pedal to move said pawl means to its release position; and a plurality of cam elements on said support means arranged concentrically to said axis and overhanging said rack means to cam said pawl means to its engagement position in response to downward swinging movement of the support means whereby pedalactuated release of said pawl means from a tooth on said rack for downward movement results in immediate engagement of the pawl means with the next successive tooth to limit the lowering of the workpiece.

3. A work holder to adjustably hold a workpiece, comprising: a base; an upwardly extending holder means to hold the workpiece; means to support said upwardly extending holder means on said base, said supporting means being mounted on the base to move about a pivot axis through a range of angles relative to the "base to vary the inclination of said holder thereby to vary the level of the workpiece; a pair of arcuate toothed racks on said support means on opposite sides of said upwardly extending holder means; a corresponding pair of pawls on said base to engage the teeth of said racks, respectively, said pawls being biased to their engagement positions; a foot pedal operatively connected to both of said pawls to move the pawls to release positions; and two series of cam elements arranged concentric to said axis adjacent said racks, respectively, to cam said pawls to their engagement positions in response to downward swinging movement of said holder means whereby pedal-actuated release of said pawls from said racks for downward swinging movement of the holder means results in immediate engagement of the pawls with the racks.

4. A work holder to adjustably hold a workpiece, comprising: a base; an upwardly extending holder means to hold the workpiece; a bearing to journal said holder means for rotation of the holder means about its longitudinal axis; means pivotally supporting said bearing on said base for movement of said bearing through an are about a transverse axis for swinging the outer end of the supporting means through a range of levels; arcuate toothed rack means on said bearing; pawl means on said base to engage the teeth of said rack means, said pawl means being biased to its engagement position; a foot pedal operatively connected to said pawl means to move the pawl means to its release position; and a plurality of cam elements positioned adjacent said rack means to cam said pawl means to its engaged position in response to downward swinging movement of the holder means whereby pedal actuated release of said pawl means from said rack means for downward swinging movement of the holder means results in immediate engagement of the pawl means with the rack means to limit the downward swinging movement of the holder means to step-by-step movement.

7 5. A mobile work holder to adjustably hold a heavy workpiece for movement from station to station along an assembly line comprising: a low level track extending along the assembly. line; a low level wheeled carriage movable along the track and engaging the track in an anti-tipping manner; means on said carriage to support a workpiece; said support means extending upwardly from the carriage and outwardly away from the track; means to journalthe lower end of said support means on the carriage for rotational adjustment of the support means about an upwardly extending axis, said journalling means being pivotally mounted on the carriage to swing said support means through an arc outwardly laterally away from the track about an axis adjacent the lower end of the upwardly extending means for raising and lowering of the workpiece; a first latch means to normally hold said journalling 111681181211 positions of adjustment of said support means along said are and when operated to release said journalling means for movement restricted to one increment of said are at a time whereby the latch means permits only. controlled step by step adjustment of the support means over said are; a first foot pedal on the carriage to operate said first latch means; a second latch means on said journalling means independent of said first latch means to releasably latch said support means relative to said journalling means at various positions of rotation relative to the journalling means; and a second foot edal on said carriage to oper'ate said second latch means. 6. A combination as set forth in claim 5 which includes means on said carriage to releasably grip said traack to immobilize the carriage at selected positions along the track.

References Cited in the file of this patent UNITED STATES PATENTS 701,167 Dennis May 27, 1902 1,453,901 Andersen May 1, 1923 1,615,860 Williams Feb. 1, 1927 1,926,828 Van Berkel Sept. 12, 1933 2,383,195 Norman Aug. 21, 1945 2,495,438 Bentley et a1 Jan. 24, 1950 2,593,738 Dol'lahite Apr. 22, 1952 2,678,714 Davis May 18, 1954 2,910,291 Courcier et a1 Oct. 27, 1959 2,929,486 Murray Mar. 22, 1960 2,983,360 Davis May 9, 1961 

1. A MOBILE HOLDER TO ADJUSTABLY HOLD A WORKPIECE FOR MOVEMENT FROM STATION TO STATION ALONG AN ASSEMBLY LINE, COMPRISING: A TRACK EXTENDING ALONG THE ASSEMBLY LINE; MEANS EXTENDING UPWARD FROM SAID CARRIAGE TO SUPPORT A WORKPIECE, SAID UPWARDLY EXTENDING MEANS BEING MOVABLE ABOUT A PIVOT AXIS RELATIVE TO THE CARRIAGE THROUGH A RANGE OF ANGLES OUTWARD TO ONE SIDE OF THE CARRIAGE; A PAIR OF ARCUATE RACKS CONCENTRIC TO SAID PIVOT AXIS, SAID RACKS FACING EACH OTHER IN SPACED RELATION TO FORM AN ARCUATE SPACE BETWEEN THE RACKS, SAID RACKS RESPECTIVELY PRESENTING SETS OF TEETH ON THE OPPOSITE SIDES RESPECTIVELY OF SAID ARCUATE SPACE WITH THE TEETH OF THE TWO SETS STAGGERED; PAWL MEANS IN SAID ARCUATE SPACE MOVABLE ALONG THE ARCUATE SPACE TO ENGAGE SAID SETS OF TEETH ALTERNATELY TO RELEASABLY HOLD SAID UPWARDLY EXTENDING MEANS AT SELECTED ANGLES IN SAID RANGE; AND A FOOT PEDAL TO OPERATE SAID PAWL MEANS FOR STEP-BY-STEP ADJUSTMENT OF SAID UPWARDLY EXTENDING MEANS THROUGH SAID RANGE. 